A Jersey City woman told police her ex-boyfriend broke into her Greenville home and attacked her with a hammer this morning, reports said.At 3:03 a.m. officers responded to the Martin Luther King Drive apartment of the 31-year-old victim and found she had swelling on her forehead, reports said.She said she was at her computer when she heard a key in her door and when it opened to the limit of the chain latch she saw her ex-boyfriend's face, reports said.After kicking in the door, he picked up a hammer and used it to knock the computer off its desk, reports said. He then punched the woman in the face before striking her on the side of her head with the hammer's handle, reports said.The man then pushed the victim to the ground and was stomping on her when she managed to get up, reports said, adding that she tried to hold him as she called police but he ran away. Police photographed swelling on the woman's face and bruising on her arm, reports said.The 30-year-old suspect has not been identified but a warrant has been issued for his arrest, reports said.